How do lice infest a human scalp? - briefly
Adult head lice grasp hair shafts near the scalp with their claws, deposit eggs on the strands, and feed on blood by piercing the skin with their mouthparts. Infestation spreads primarily through direct head‑to‑head contact or by sharing personal items such as combs, hats, or pillows.
How do lice infest a human scalp? - in detail
Lice colonize a human head by exploiting direct contact and favorable conditions on the scalp. Adult females lay eggs (nits) near the hair shaft, usually within one centimeter of the scalp where temperature and humidity support embryonic development. The glue‑like cement they secrete secures each nit to the cuticle, making removal difficult.
After hatching, nymphs emerge and immediately begin feeding on blood from the scalp. Their mandibles pierce the epidermis, drawing small quantities of blood that cause irritation and itching. Feeding occurs several times a day, providing the nutrients required for rapid growth. Nymphs molt three times before reaching adulthood, a process that takes about 9–12 days under optimal conditions.
Transmission relies on close head‑to‑head contact, which transfers mobile adults and nits. Indirect spread can occur via shared items such as combs, hats, or pillows, though the likelihood is lower because lice cannot survive long off a host. Once on a new host, the cycle repeats: females locate suitable oviposition sites, lay eggs, and the population expands exponentially if untreated.
Key factors that facilitate infestation include:
- Warm, moist environment of the scalp.
- Dense hair that offers shelter and maintains humidity.
- Frequent direct contact among individuals, especially children.
- Lack of timely detection and removal of eggs and nymphs.
Effective control requires simultaneous removal of live insects and their eggs, often through combing with a fine‑toothed lice comb, followed by repeated treatments to eliminate newly hatched nymphs. Chemical pediculicides, when used according to guidelines, can reduce the adult population, but resistance has been documented, making mechanical removal essential. Continuous monitoring for at least two weeks after treatment confirms eradication.